improved IsEmptyOrNull implementation

src/Aardvark.Base/Extensions/IEnumerableExtensions.cs

@@ -876,14 +876,13 @@ public static bool AllEqual<T>(this IEnumerable<T> elements)
         #region Comparisons
 
         /// <summary>
-        /// Implemented in System.Interactive.dll.
         /// Returns true if elements contains no items or if elements is null,
         /// false otherwise.
         /// </summary>
         public static bool IsEmptyOrNull<T>(this IEnumerable<T> elements)
         {
             if (elements == null) return true;
-            return elements.Take(1).Count() == 0;
+            return !elements.Any(); // will check for ICollection<T> internally
         }
 
         public static IEnumerable<T> NonNull<T>(IEnumerable<T> elements)